This application claims the benefit of Korean Patent Application No. 1999-63249, filed on Dec. 28, 1999, under 35 U.S.C. xc2xa7119, the entirety of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly to a method of manufacturing an array substrate for use in a reflective LCD device.
2. Description of Related Art
Liquid crystal display (LCD) devices are in wide use as display devices capable of being reduced in weight, size and thickness. In general, the LCD device includes upper and lower substrates with a liquid crystal layer interposed therebetween. The upper substrate includes a common electrode and a color filter, and the lower substrate includes a pixel electrode and TFTs. An upper polarizer is arranged on a front surface of the upper substrate, and a lower polarizer is arranged on a bottom surface of the lower substrate. A back light device is arranged under the lower substrate as a light source.
The LCD device is divided into a transmissive LCD device and a reflective LCD device. The typical transmissive LCD device displays images using light from the back light device. However, the transmissive LCD device is a non-effective light converter that merely transmits about 3% to about 8% of light from the back light device. In other words, as shown in FIG. 1, an observer gets to see about 7% of light from the back light device. Therefore, the transmissive LCD device requires a back light device having a high brightness, leading to a high power consumption.
In order to achieve the back light device having a high brightness, a sufficient power must be supplied to the back light device, thereby increasing a battery weight. However, even such a back light device can not be used for a long time.
To overcome the problems described above, the reflective LCD device has been introduced. Since the reflective LCD device is driven using ambient light, the power consumption becomes lower, whereby it is possible to use it for a long time and it is easy to carry due to its light weight.
FIG. 2 is a plan view illustrating a lower array substrate of a conventional reflective LCD device. As shown in FIG. 2, data lines 2 and 4 are arranged in a longitudinal direction, and gate lines 6 and 8 are arranged in a transverse direction perpendicular to the data lines 2 and 4. A reflective electrode 10 is arranged on a region defined by the gate and data lines. TFTs are arranged at a cross point of the gate and data lines. Each of the TFTs includes a gate electrode 18, a source electrode 12 and a drain electrode 14. The gate electrode 18 extends from the gate line 8, and the source electrode 12 extends from the data line 2. The drain electrode 14 is spaced apart from the source electrode 12 and contacts the reflective electrode 10 through a contact hole 16.
FIG. 3 is a cross sectional view taken along line IIIxe2x80x94III of FIG. 2. As shown in FIG. 2, the gate electrode 18 is formed on a substrate 1, and a gate insulating layer 20 is formed on the gate electrode 18 and an exposed surface of the substrate 1. A semiconductor layer 22 is formed on the gate insulating layer 20. The source and drain electrode 12 and 14 overlaps both end portions of the semiconductor layer 22. A passivation film 24 is formed over the whole surface of the substrate 1 while covering the source and drain electrodes 12 and 14. The passivation film 24 has the contact hole 16 on a portion of the drain electrode 14. The reflective electrode 10 is formed on the passivation film and contacts the drain electrode 14 through the contact hole 16. The reflective electrode is made of a material having a good reflectance.
As described above, since the reflective LCD device uses ambient light other than an internal light source such as a back light device, it can be used for a long time. In other words, the reflective LCD device is driven using light reflected from the reflective electrode 10.
However, as shown in FIG. 3, the reflective electrode 10 has a flat structure, and thus a mirror effect may occur when an observer views images displayed by the reflective electrode 10. In other words, a face of an observer may be reflected by the flat reflective electrode 10 due to the flatness of the flat reflective electrode 10. Further, since no back light but ambient light is used, the brightness is relatively low.
In order to overcome the problems described above, as shown in FIG. 4, a reflective electrode having concave or convex portions 30 has been introduced. The reflective electrode 10 having the concave or convex portions 30, as shown in FIG. 5, causes diffuse reflection, thereby reducing the mirror effect. In addition, since the reflection area of the reflective electrode 10 increases due to the thickness of the reflective electrode 10, the brightness increases. Typically, in order to form the concave or convex portions 30 of the reflective electrode 10, the passivation film 24 and the insulating layer 20 at a pixel portion are etched through using at least two mask processes. Therefore, the manufacturing process increases in number, and the manufacturing yield is lowered.
For the foregoing reasons, there is a need for a reflective liquid crystal display device having a high brightness and a high manufacturing yield that is manufactured by a simple process.
To overcome the problems described above, preferred embodiments of the present invention provide a reflective liquid crystal display device having a high brightness and a high manufacturing yield that is manufactured by a simple process.
In order to achieve the above object, the preferred embodiments of the present invention provide a method of manufacturing an array substrate for use in a reflective liquid crystal display device, including: providing a thin film transistor array substrate; depositing a metal layer on the substrate using a shadow mask having a plurality of holes; and patterning the metal layer into a reflective electrode for connecting to the thin film transistor.
The present invention further provides a method of manufacturing an array substrate for use in a reflective liquid crystal display device, including: providing deposition equipment having a sputtering target, a thin film transistor array substrate, and a mask, the mask having a plurality of holes and located between the sputtering target and the substrate; depositing a metal layer on the substrate by allowing metal particles generated from the target to pass through the holes; and patterning the metal layer into a reflective electrode.
The holes of the mask have one of a trapezoid, a circular and a rectangular cross section.
A mask is used to form a reflective electrode of a reflective LCD device according to the preferred embodiment of the present invention, since an additional process to form the concave or convex portion is not required, and the manufacturing process is simplified, thereby increasing a manufacturing yield. In addition, since the reflective electrode has concave or convex portions, the brightness can increase.